For expository convenience the present invention will be illustrated with reference to a paging system (the "Gaskill system") described in U.S. Pat. Nos. 4,713,808 and 4,897,835. However, it will be understood that the present invention is not so limited. The disclosures of U.S. Pat. Nos. 4,713,808 and 4,897,835 are incorporated herein by reference.
For purposes of the present discussion, it will be understood that the Gaskill system provides a paging system wherein a paging device is incorporated into a wristwatch. Paging information, together with time of day information, is transmitted by FM radio signal to each watch according to a time slot protocol. In accordance with this protocol, the watch includes a timing mechanism for activating a radio receiver and decoder of the watch during a time slot selected by the watch. The watch thereby activates its radio receiver and decoder to capture the radio signal data broadcast during its selected time slot.
A watch using the Gaskill system can maintain a higher degree of accuracy than a conventional time piece. For example, with a conventional time piece, even the slightest inaccuracy in its time keeping reference can be cumulative. The extent of error, or deviation from the actual time tends to grow over time. With a number of conventional time pieces placed side by side, the least significant digits, e.g., the seconds digits, will not change in synchronization. Even if conventional time pieces are set initially to identical time, the slightest inaccuracy in time keeping accumulates making impossible synchronized time displays.
Thus, inaccuracy of a time piece is observed by inspecting the time displayed by a number of such time pieces placed side by side. If the time pieces keep accurate time, this is reflected in simultaneous display updates by all time pieces. For example, the seconds display for all devices will change simultaneously if time is maintained accurately by all devices. Typically, however, such simultaneous display updating is not achieved, and if achieved such condition does not endure.
Accordingly, it is desirable to provide an accurate time keeping device whereby a group of such devices maintains time accurately and exhibits such accuracy by continued simultaneous display updating.